Infrared-active defects in irradiated Czochralski-type and float-zone material were investigated, after annealing at 450C, by using infra-red absorption and electrical methods. By introducing thermal donors in order to alter the position of the Fermi level, the defect which was associated with the higher-order bands could be analyzed. The results indicated that the optically active higher-order bands were associated with the slow relaxation of photo-excited carriers.

Y.Shi, M.Suezawa, F.M.Wu, M.Imai, Y.D.Zheng, K.Sumino: Materials Science Forum, 1995, 196-201, 157-62